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参数资料
| 型号： | M41T00 |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 时钟/数据恢复及定时提取 |
| 英文描述： | 1 TIMER(S), REAL TIME CLOCK, PDSO8 |
| 封装： | 0.150 INCH, PLASTIC, SO-8 |
| 文件页数： | 15/15页 |
| 文件大小： | 96K |
| 代理商： | M41T00 |
CLOCK CALIBRATION
The M41T00 is driven by a quartz controlled oscil-
lator with a nominal frequency of 32,768 Hz. The
devices are tested not to exceed 35 ppm (parts per
million) oscillator frequency error at 25
°C, which
equates to about
± 1.53 minutes per month. With
the calibration bits properly set, the accuracy of
each M41T00 improves to better than +2/–1 ppm
at 25
°C.
The oscillation rate of any crystal changes with
temperature (see Figure 14). Most clock chips com-
pensate for crystal frequency and temperature shift
error with cumbersome trim capacitors. The
M41T00 design, however, employs periodic
counter correction. The calibration circuit adds or
subtracts counts from the oscillator divider circuit
at the divide by 256 stage, as shown in Figure 13.
The number of times pulses are blanked (sub-
tracted, negative calibration) or split (added, posi-
tive calibration) depends upon the value loaded
into the five bit Calibration byte found in the Control
Register. Adding counts speeds the clock up, sub-
tracting counts slows the clock down.
The Calibration byte occupies the five lower order
bits (D4-D0) in the Control register (Addr 7). This
byte can be set to represent any value between 0
and 31 in binary form. Bit D5 is a Sign bit; ’1’
indicates positive calibration, ’0’ indicates negative
calibration. Calibration occurs within a 64 minute
cycle. The first 62 minutes in the cycle may, once
per minute, have one second either shortened by
128 or lengthened by 256 oscillator cycles. If a
binary ’1’ is loaded into the register, only the first 2
minutes in the 64 minute cycle will be modified; if a
binary 6 is loaded, the first 12 will be affected, and
so on.
Therefore, each calibration step has the effect of
adding 512 or subtracting 256 oscillator cycles for
every 125,829,120 actual oscillator cycles, that is
+ 4.068 or –2.034 ppm of adjustment per calibra-
tion step in the calibration register. Assuming that
the oscillator is in fact running at exactly 32,768 Hz,
each of the 31 increments in the Calibration byte
would represent +10.7 or –5.35 seconds per month
which corresponds to a total range of +5.5 or –2.75
minutes per month.
AI00602
R/W
SLAVE ADDRESS
START
A
0
100
0
11
MSB
LSB
Figure 9. Slave Address Location
AI00589
SDA
P
tSU:STO
tSU:STA
tHD:STA
SR
SCL
tSU:DAT
tF
tHD:DAT
tR
tHIGH
tLOW
tHD:STA
tBUF
S
P
Figure 8. Bus Timing Requirements Sequence
Note: P = STOP and S = START
9/15
M41T00
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相关代理商/技术参数 |
参数描述 |
|---|---|
| M41T00_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Serial real-time clock |
| M41T00AUD | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Serial real-time clock with audio |
| M41T00AUD_12 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Serial real-time clock (RTC) with audio |
| M41T00AUDD1E | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Serial real-time clock with audio |
| M41T00AUDD1F | 功能描述:实时时钟 SERIAL RTC W/AUDIO RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
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